Celica L4-122 1998cc 2.0L DOHC Turbo (3S-GTE) (1990)
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Ignition Coil: Description and Operation
Primary Coil Test
The ignition coil uses the principle of mutual induction to step up battery (low) voltage to ignition (high) voltage. The ignition coil contains two sets of
copper wire windings around a soft iron core. The primary winding is made of a hundred or so turns of a heavy gauge wire. It is connected to the battery
so that current flows through it, thus creating a magnetic field.
When current flow in the primary winding is stopped (by the igniter breaking the circuit ground), the collapse of the magnetic field causes a high voltage
(20,000 volts or more) to be induced in the secondary windings. The number of turns in the secondary winding is proportionally higher than the number
of turns in the primary winding, depending on the desired output voltage. The ratio is approximately 1 to 110.
The high voltage pulse then flows through the coil wire to the distributor.
